This thesis is about the legal and moral status of abortion. It is primarily concerned with the metaphysical status of the foetus, with particular attention to the question whether the foetus is properly characterised as a person in the philosophical sense. The argument of the thesis proceeds in two parts. The first part surveys certain lines of argument to the effect that the question of prenatal personhood is immaterial to the moral and legal permissibility of abortion. Against these claims, it argues that the personhood status of the foetus is indeed central to the moral and legal appraisal of abortion practice. The second part focuses on the metaphysical question in its own right. The thesis proposes a theoretical underpinning for the ‘gradualist’ view of human life before birth, according to which the human foetus is a fuller instantiation of a person the more biologically developed it is. It sets out to defend the kernel of the gradualist thesis against a cluster of criticisms, commonly advanced by those who endorse the belief that the personhood of human beings begins at conception. One notable challenge of this sort, which the thesis aims to address, asserts that any graduated account of personhood before birth is logically inconsistent with basic human equality. Finally, the thesis considers a few practical implications for the legal regulation of abortion stemming from the gradualist thesis, and the rule of law standards by which a regulatory framework must abide.